the easiest way is to click on the character, and keep him highlighted. Then use tilde key and type give_trait "This" traitname.Example: give_trait "This" GoodCommander 5 or give_trait "This" HaleAndHearty 3

Some traits only go to level 3 and 5 is max, you can do a search for different traits. Using "This" instead of character's name is alot easier than remembering their full names.